This invention relates to the serious dangers associated with persons breathing particulate contaminated air. This invention is particularly useful for protecting the outside environment and the individuals working in a highly contaminated area such as occurs when asbestos coatings are being removed inside a building structure. Asbestos fibers fall into the generic classification of hazardous particulate and are a well known carcinogenic hazard to humans and animals. Typical environmental standards refer to fibers that are 5 microns or greater in length with an aspect ratio of 3 to 1 or greater. The standards presently in use utilize a phase contrast optical microscope with about 440 magnification. These testing methods are not capable of seeing fibers below about 0.3 micron in diameter. Actually, the average asbestos fiber is about 0.1 micron in diameter. Therefore, using the present standards and equipment, for every fiber counted there is present as many as 30 fibers uncounted. This is coupled with the standard that fibers shorter than 5 microns in length are not considered. It is now accepted that the thinner fibers are the most dangerous threat to human health. While present standards indicate "satisfactory condition" with concentrations less than 2.0 fibers per cubic centimeter, this, in reality, means that the standards allow an actual concentration of about 60 fibers per cubic centimeter, if the thinner fibers were counted. The asbestos fibers, in particular those that are thinner and shorter remain airborne for considerable lengths of time and contaminate large volumes of air to form a substantial hazard to the environment and to the persons working or living in the area. A typical requirement standard of requiring that the area "settle" for 24 hours before allowing persons to re-enter in order to clean up settled asbestos fibers is clearly insufficient for protection. The thinner fibers remain airborne for up to 80 hours and it is now clear that re-entry into the room stirs up the fibers to pose the same hazard. Wet removal processes for removal of an offending coating containing asbestos fibers utilize a "wetting down" process of the removed coating. It is now clear that this process still allows large amounts of fibers to enter and remain in the surrounding air space. New proposed standards provide for reduction and maintenance of a fiber level to 0.1 fibers per cubic centimeters of air using the optical microscope techniques. Scanning electron microscopes indicate that even at that reduced level there is in reality about 3 fibers per cubic centimeter including the thinner and smaller fibers. My invention is particularly directed to reducing the hazards involved with either dry or wet removal of asbestos containing material and is aimed at reducing the fiber content to 0.01 fibers per cubic centimeter including the thin and shorter fibers as small as 0.1 microns diameter and 2 microns in length, using a scanning electron microscope (sem) with a 6,000 to 10,000 magnification.
While most of the description of my method and the devices used sith the method relate to control of asbestos fiber contamination, it should be understood that my method and device can be used to protect the workers and the outside environment from a wide variety of offending particulate contamination.
Many asbestos removal projects relate to buildings or large rooms that have substantial logistical problems such that the ability to seal off the area is prevented. Systems have been provided that attempt to seal off the room, or the building from the outside environment such that when the job is completed, all of the contamination will have been kept within a certain area. However, buildings are typically not designed to be absolutely sealed off, leaks occur and the outside environment is contaminated. Further, during the removal, the workers are subjected to a substantial risk due to the high concentration build-up.
Air purifiers in a variety of configurations have been available for some time. In particular, air filtration systems have been equipped with a plenum attachment to provide a "source capture" fume collector such as those used to remove welding smoke and fumes from soldering, welding, or brazing locations. These air purifiers are provided with a non-collapsible duct work which has its entrance point close to the area of contamination. Plenums can provide for one or two inlets for more than one welding location. Filter systems with a series of filters in the flow line provide what is described as near complete filtration of particulate out of the air stream.
U.S. Pat. No. 3,334,597 to F. R. Ruskin, et al, describes a radiation-proof structure, wherein a self-contained air generating and re-generating unit provides required air when the shelter is closed up tight in use. U.S. Pat. No. 4,178,159 to Fecteau describes a clean room filter assembly to provide a totally sealed air delivery system for a clean room. In U.S. Pat. No. 2,710,574, H. E. Runion decribes a room in which there are one or more machines or devices which produce paper dust or similar atmospheric matter which is desirable to remove. His system is a filter medium device. U.S. Pat. No. 4,040,042, to Horst Mayer describes an exhaust apparatus and monitoring circuit therefor to monitor the operation of the fan in response to contamination of the filter. U.S. Pat. No. 2,838,130 to L. E. Lemmon describes an air conditioner that will automatically shut off the air into the compartment of an auto. C. E. Hollingsworth in U.S. Pat. No. 2,299,620 describes a series of filters, one for low veocity dust, one for electrostatic type and the final one being an adsorbent type. An air filtering apparatus is described in U.S. Pat. No. 3,936,284 to Donald G. Mason with a filter system of spun fiberglass mat/adsorptive charcoal and a HEPA-type filter panel. The HEPA type filter is an acronym for High Efficiency Particulate air filter as covered by Federal Standard 209 and Military Standard 282 and described in U.S. Pat. No. 3,498,032, incorporated herein by reference. This type of filter is also known in the industry as the "absolute" filter. U.S. Pat. No. 4,175,934 to Arnold Lang describes a "clear air device" utilizing a preliminary filter and a HEPA filter. U.S. Pat. No. 4,191,543 to Max D. Peters also describes an apparatus using a HEPA filter.
None of the prior art having satisfied the needs in the industry to protect the workers in an area of highly dangerous particulate level and, in particular, high asbestos fiber levels, the following are objects of my invention:
An object of my invention is to provide a method of containing, lowering, and essentially eliminating the danger of asbestos inhalation by workers in a building in which asbestos fibers are being generated at extremely high levels.
It is a further object of this invention to provide a method of protecting the outside environment from asbestos particulate contamination during the removal of asbestos coatings from the inside walls of the building, despite the fact that the area targeted for coating removal cannot be made air-tight.
An additional object of this invention is to prevent asbestos fiber release into the outside environment that might occur in an unforseen accident such as a leak through a damaged barrier.
A further object of this invention is to remove the offending particulate away from workers breathing zones while they work toward cleanup of the building, such that more comfortable half-face respirators may be used by the workers.
An additional object of this invention is to reduce the overall fiber counts in the work area generating high quantities of asbestos fibers into the air.
An additional object of this invention is to reduce the humidity and heat build up inside the barrier where the asbestos cleanup is taking place so that the necessary safety clothing does not become intolerable.
It is a further object of this invention to provide a filtration unit that is portable in size and easy to handle.
It is an additional object of this invention to provide a filtration device that provides easy access to disposable filters.
It is a further object of this invention to provide warning lights to indicate proper functioning of the filters, automatic shut-down with a warning light when a filter is not in place and a filter becomes ineffective or the exhaust is obstructed Further indicators should show the air delivery and a warning light to indicate reduced air flow due to dirty filter or obstructed intake still allowing time to shut down before any contamination takes place.
It is an additional object of this invention to provide a filtration device which indicates the accumulated time of operation with the filter in place so as to be able to remove the course filter before the finer filters are clogged.
It is an additional object of this invention to provide a filtration device and method wherein the personnel can depart from the work area, complete the decontamination process without subjecting them to a down time when the air is not being filtered.
It is an additional object of this invention to provide a filtration device which will draw off high fiber concentration from an immediate work area wherein covering the entire room is impractical.
It is a further object of this invention to provide a method and a filtration device which will provide working conditions wherein the contaminating particulate is always being continuously drawn away from the worker and not past the worker before being removed from the work area.
It is a further object of this invention to draw airborne asbestos fibers to the filtration system rather than allowing the fibers to circulate within the work area and settling back into the clean areas within the work area or in the outside environment.